Lack of portal-venous hypertension after an arterioportal fistula in the rat.

The hepatic effects of an end-to-side arteriovenous fistula between the right renal artery and the portal vein were studied in rats. Fifty rats underwent surgery and were studied 3, 12, 24 weeks and 1 year later; Another 15 rats were used as controls. Rats did not have any portohepatic abnormality. Portal and caval pressure were measured, and the liver was evaluated histologically. No statistically significant differences were achieved between the control portal (10.37 +/- 0.29 cm H2O) and vena cava pressures (1.22 +/- 0.19 cm H2O) and those of the experimental groups. The overall liver architecture remained unchanged. A progressive enlargement of the intrahepatic portal and hepatic veins was noted. No hypertrophy of the fibrous tissue into the portal triads, hypertrophy of the muscularis of the portal vein radicals, or wall sclerotic thickening was seen. The forward overflow compensatory mechanisms are discussed.